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Children who watch too much television could be overstimulating their brains, think real life is boring in comparison, and be missing out on activities such as reading and sport which promote and encourage concentration.
A ground-breaking new study from Otago University has found that children who watch too much television are more likely to have difficulty paying attention when they are teenagers.
The study is the first in the world to look at the possible long-term link between television viewing in childhood and attention problems in adolescence.
Researchers found children who watched more than two hours of television a day (and particularly those who watched more than three hours) had above-average symptoms of attention problems in adolescence.
Symptoms included short attention span, poor concentration and being easily distracted.
The findings could not be explained by early-life attention difficulties, socio-economic factors or intelligence.
The findings, published in the latest issue of the US journal Pediatrics, come out of the Dunedin Multidisciplinary Health and Development Study at the University of Otago.
Co-author Dr Bob Hancox said the findings suggested childhood television viewing may contribute to the development of attention problems.
He said the findings supported the recommendation of the American Academy of Pediatrics to limit children's television viewing to a maximum of two hours per day.
"Although teachers and parents have been concerned that television may be shortening the attention span of children, this is the first time that watching television has been linked to attention problems in adolescence," said Dr Hancox, who is also Deputy Director of the Dunedin Multidisciplinary Health and Development Research Unit.
"This latest study adds to the growing body of evidence that suggests parents should take steps to limit the amount of TV their children watch."
He said it wasn't just television viewing time that should be limited, but screen time of any kind, including computer and DVD time.
The study cited several possible explanations for the connection between television and attention problems.
The first is that the rapid image and scene changes may overstimulate children and affect brain development, particularly in younger children, whose brains are less developed. "People's brains get trained to expect everything to change very rapidly ... so it's very difficult to hold your attention," said Dr Hancox.
The second is that life on television, with its fast-paced editing and attention-grabbing techniques, makes real life seem boring. Children who watch a lot of television become less tolerant of slower-paced activities such as homework.
Watching television may also supplant activities such as reading and sport, which teach children to pay attention.
Also, inattention may be a conditioned response. "Television programmes will continue, regardless of the attentional input from the viewer. Therefore, children may learn that they can divert their attention when watching television. This learned response might generalise to other activities," the study said.
The researchers said the study did not prove that watching television caused attention problems in adolescents, because it was possible that children with attention problems simply chose to watch more television.
"However, our results show that the net effect of television seems to be adverse," the study said.
The study followed more than 1000 children born in Dunedin between April 1972 and March 1973.
The amount of time they spent watching television was recorded every two years between the ages of 5 and 11. Attention problems were reported by the children themselves, and their parents and teachers.
Previous studies by the unit have linked children's excessive television viewing to obesity, a range of health problems in young adulthood, as well as lower educational achievement.
